Combustion power source with back pressure release for combustion powered fastener-driving tool

Abstract

A combustion tool includes a cylinder having a lower end provided with a resilient bumper, a piston dimensioned for reciprocation within the cylinder to impact the bumper at an end of the cylinder and having a driver blade depending therefrom for impacting fasteners. At least one back pressure release opening is disposed in the cylinder to be in alignment with the piston and to be closed by the piston when the piston impacts the bumper.

1. A fastener driving tool, comprising:
 a cylinder having a lower end provided with a resilient bumper; 
 a piston dimensioned for reciprocation within said cylinder to impact said bumper at an end of said cylinder and having a driver blade depending therefrom for striking fasteners; and 
 at least one back pressure release opening disposed in said cylinder to be in alignment with said piston, each said opening being closed by said piston to seal said cylinder from air loss as said piston impacts said bumper, 
 wherein said at least one back pressure release opening is constructed and arranged so that upon said piston impacting said bumper and closing said at least one opening, a residual volume of air is trapped in said sealed cylinder below said piston to dampen impact of said piston upon said bumper. 
 
     
     
       2. The tool of  claim 1  further including a plurality of said openings spaced about said cylinder. 
     
     
       3. The tool of  claim 1  wherein said at least one opening is dimensioned to have a height approximately less than or equal to a height of said piston. 
     
     
       4. The tool of  claim 3  wherein said piston has a pair of spaced seal rings, and said at least one opening has a height less than or equal to a distance between said rings so that at least one of an upper seal ring seals an upper margin of said at least one opening, and a lower seal ring seals a lower margin of said at least one opening as said piston impacts said bumper. 
     
     
       5. The tool of  claim 1  wherein said at least one release opening is constructed and arranged so that when said piston impacts said bumper, said cylinder is sealed from ambient air loss, both above and below said piston. 
     
     
       6. The tool of  claim 1  wherein said bumper is provided with a generally normal profile of an upper exterior dimension which increases bumper volume. 
     
     
       7. The tool of  claim 1  further including a dampening formation provided to a lower side of said piston. 
     
     
       8. The tool of  claim 7  wherein said dampening formation has a shape which complements a profile of said bumper. 
     
     
       9. A fastener driving tool, comprising:
 a cylinder having a lower end provided with a resilient bumper; 
 a piston dimensioned for reciprocation within said cylinder and having a driver blade depending therefrom for impacting fasteners, and a pair of spaced seal rings; and 
 at least one back pressure release opening disposed in said cylinder for releasing back pressure on said piston and having a height approximately less than or equal to a height of said piston, said piston configured to block each said opening to seal said cylinder from air loss as said bumper is impacted for retaining a residual volume of air for providing dampening to said piston, 
 said at least one opening having a height less than or equal to a distance between said rings so that at least one of an upper seal ring seals an upper margin of said at least one opening, and a lower seal ring seals a lower margin of said at least one opening as said piston impacts said bumper. 
 
     
     
       10. The tool of  claim 9  wherein said at least one back pressure release opening is disposed on said cylinder to be closed by said piston as said piston impacts said bumper. 
     
     
       11. The tool of  claim 9  wherein said bumper is provided with a generally normal profile of an upper exterior dimension which increases bumper volume. 
     
     
       12. The tool of  claim 9  further including a dampening formation provided to a lower side of said piston which complements an opposing profile of said bumper. 
     
     
       13. A method for reducing combustion-generated back pressure in a combustion tool including a cylinder having a lower end provided with a resilient bumper, a piston dimensioned for reciprocation within the cylinder and having a driver blade depending therefrom for impacting fasteners, and at least one back pressure release opening disposed in the cylinder for releasing back pressure On the piston, said method comprising:
 positioning the at least one back pressure release opening to correspond with a position of the piston as it impacts the bumper, wherein each said opening is blocked by said piston to seal the cylinder from air loss upon said impact of the bumper; and 
 reducing a volume defined between the piston and the lower end of the cylinder by increasing at least one of piston profile and bumper profile. 
 
     
     
       14. The method of  claim 13  further including providing said piston with at least one seal ring constructed and arranged to maintain a sealing relationship with the cylinder above the at least one back pressure release opening to maintain a seal as the piston impacts, compresses and returns from the bumper. 
     
     
       15. The method of  claim 13  further including providing said piston with at least one seal ring constructed and arranged to maintain a sealing relationship below the at least one back pressure release opening to maintain a seal as the piston impacts, compresses and returns from the bumper. 
     
     
       16. The method of  claim 13  further including providing said piston with at least one seal ring constructed and arranged to maintain a sealing relationship above the at least one back pressure release opening to maintain a seal as the piston impacts, compresses and returns from the bumper, and at least one seal ring constructed and arranged to maintain a sealing relationship below the at least one back pressure release opening to maintain a seal as the piston impacts, compresses and returns from the bumper.